Minah Suh

Sungkyunkwan University, Sŏul, Seoul, South Korea

Are you Minah Suh?

Claim your profile

Publications (39)118.05 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Parkinson's disease (PD) is characterized by progressive dopaminergic cell loss in the substantia nigra (SN) and elevated iron levels demonstrated by autopsy. Direct visualization of iron with live imaging techniques has not yet been successful. The aim of this study is to visualize and quantify the distribution of cellular iron using an intrinsic iron hyperspectral fluorescence signal. The 1-methyl-4-phenylpyridinium (MPP+)-induced cellular model of PD was established in SHSY5Y cells exposed to iron with ferric ammonium citrate (FAC, 100 μM). The hyperspectral fluorescence signal of iron was examined using a high-resolution dark-field optical microscope system with signal absorption for the visible/near infrared spectral range. The 6-h group showed heavy cellular iron deposition compared with the 1-h group. The cellular iron was dispersed in a small particulate form, whereas the extracellular iron was aggregated. In addition, iron particles were found to be concentrated on the cell membrane/edge of shrunken cells. The iron accumulation readily occurred in MPP+-induced cells, which is consistent with previous studies demonstrating elevated iron levels in the SN. This direct iron imaging could be applied to analyze the physiological role of iron, and its application might be expanded to various neurological disorders involving metals, such as copper, manganese, or zinc.
    Journal of Biomedical Optics 05/2014; 19(5):51207. · 2.88 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: We studied the electrophysiological, hemodynamic, and cytomorphological consequences of microhemorrhagic brain injury induced by a nanoscale iron injection. Of particular interest were the etiology, development, and treatment of epilepsy associated with this injury. We developed an animal model of chronic epilepsy using nanoscale injection into the adult mouse cortex. Although injection of nanoamounts of iron did not cause clear cell death or damage in the cortex, it elicited varying degrees of spontaneous epileptiform events that could be recorded under anesthesia 3 months postinjection. The influence of these chronic epileptiform events on neurovascular coupling was probed by directly stimulating the cortex ipsilateral to the epileptic focus and by measuring cerebral blood volume simultaneously in both hemispheres using intrinsic signal optical imaging. The ipsilateral hemodynamic response was dramatically lower in animals that exhibited longer, more frequent epileptiform events, but it was unchanged in animals displaying infrequent, short events. In contrast, the contralateral hemodynamic response was augmented in all iron-injected animals compared with the control group. These abnormal hemodynamic responses in chronically epileptic animals were correlated with the degree of reduction in the number of GABAergic interneurons. Therefore, nanoscale iron injection, which mimics some aspects of microhemorrhagic brain injury, generated chronic, yet varying, degrees of spontaneous epileptiform events. Moreover, the severity of the epileptiform events corresponded to the degree of reduction in GABAergic interneurons in the iron-injected hemisphere and the level of autoregulatory dysfunction of cerebral blood flow. © 2013 Wiley Periodicals, Inc.
    Journal of Neuroscience Research 12/2013; · 2.97 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Recent advances in biotechnology and imaging technology have provided great opportunities to investigate cellular dynamics. Conventional imaging methods such as transmission electron microscopy, scanning electron microscopy, and atomic force microscopy are powerful techniques for cellular imaging, even at the nanoscale level. However, these techniques have limitations applications in live cell imaging because of the experimental preparation required, namely cell fixation, and the innately small field of view. In this study, we developed a nanoscale optical imaging (NOI) system that combines a conventional optical microscope with a high resolution dark-field condenser (Cytoviva, Inc.) and halogen illuminator. The NOI system's maximum resolution for live cell imaging is around 100 nm. We utilized NOI to investigate the dynamics of intracellular microvesicles of neural cells without immunocytological analysis. In particular, we studied direct, active random, and moderate random dynamic motions of intracellular microvesicles and visualized lysosomal vesicle changes after treatment of cells with a lysosomal inhibitor (NH4Cl). Our results indicate that the NOI system is a feasible, high-resolution optical imaging system for live small organelles that does not require complicated optics or immunocytological staining processes.
    Journal of Nanoscience and Nanotechnology 11/2013; 13(11):7229-34. · 1.15 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We report the application of an optical microscope equipped with a high-resolution dark-field condenser for detecting dynamic responses of cellular nanostructures in real time. Our system provides an easy-to-use technique to visualize biological specimens without any staining. This system can visualize the dynamic behavior of nanospheres and nanofibers, such as F-actin, at the leading edges of adjacent neuronal cells. We confirmed that the nanofibers imaged with this high-resolution optical microscopic technique are F-actin by using fluorescence microscopy after immunostaining the F-actin of fixed cells. Furthermore, cellular dynamics are enhanced by applying noncontact electric field stimulation through a transparent graphene electric field stimulator. High-resolution label-free optical microscopy enables the visualization of nanofiber dynamics initiated by filopodial nanofiber contacts. In conclusion, our optical microscopy system allows the visualization of nanoscale cellular dynamics under various external stimuli in real time without specific staining.
    Journal of Biomedical Optics 06/2013; 18(6):66016. · 2.88 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Enhancing cerebral blood volume (CBV) of a targeted area without causing side effects is a primary strategy for treating cerebral hypoperfusion. Here, we report a new non-pharmaceutical, and non-vascular surgical method to increase CBV. A flexible, transparent, and skin-like biocompatible graphene electrical field stimulator (GEFS) was placed directly onto the cortical brain and a non-contact electric field was applied at a specific local blood vessel. Effective CBV increases in the blood vessels of mouse brains were directly observed from in vivo optical recordings of intrinsic signal (ORIS) imaging. The CBV was significantly increased in arteries of the stimulated area, but neither tissue damage nor unnecessary neuronal activation was observed. No transient hypoxia was observed. This technique provides a new method to treat cerebral blood circulation deficiencies at local vessels and can be applied to brain regeneration and rehabilitation.
    ACS Nano 05/2013; · 12.03 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The two major circulatory systems, the lymph system and the blood vessel system, play significant roles in controlling embryonic development. The primo-vascular system (PVS) was recently reported as an additional circulatory system in various animals. In this paper, the PVS in a mouse embryo was investigated. The structural characterization of the PVS in the mouse placenta and umbilical cord, which was visualized with the trypan blue staining technique, was focused on. The PVS was well_developed in the mouse placenta area. Using a nanopore-based amperometric oxygen sensor, the oxygen levels at four different areas of the embryonic brain, placenta, blood vessel, and primo-vessel of the PVS were measured. The relatively higher oxygen levels that were measured at the primo-vessels than at the brain and the placenta, while still lower than the oxygen level that was measured at the blood vessels, may suggest a role of PVS in oxygen transport.
    Journal of Nanoscience and Nanotechnology 07/2012; 12(7):5168-72. · 1.15 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Mobility is one of the important characteristics of living cells. It also plays a significant role in therapeutic cell transplantation with target location specificity. To enhance cell mobility, a neural cell stimulator was assembled with graphenes, which are two-dimensional nanocarbon materials that form a transparent electrode over the cover glass in a cell culture dish. This transparent stimulator applies electrical field stimulation to the neural cells. The advantages of this new transparent electrical field stimulator (TEFS) with a graphene electrode include transparency, because few layered graphenes are optically transparent, and biocompatibility, because the cover glass is coated with laminin. In this paper, it is reported that constant electric field stimulation, which is at a specific strength, facilitates the mobility of a neural cell and makes the visibility of cellular behavior on the electrode much better than that of any other existing cell stimulator that has metal electrodes. The strength of the electrical field for stimulating cells varies from 4.5 mV/mm to 450 mV/mm. When continuous electric field stimulation was applied for 4 hours at the electric field strength of 45 mV/mm, the mobility of the neural cells was significantly enhanced compared to the control conditions, wherein there was no electric field stimulation. Thus, the feasibility of the TEFS with the nanothickness of graphene was tested to modulate the mobility of neural cells in vitro. The result suggests that electrical field stimulation could enhance neural cell alignment, cell-to-cell coupling, and networks, and may be applied to cell transplantation to boost therapeutic effectiveness.
    Journal of Nanoscience and Nanotechnology 07/2012; 12(7):5222-7. · 1.15 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We studied depth-dependent cerebral hemodynamic responses of rat brain following direct cortical electrical stimulation (DCES) in vivo with optical recording of intrinsic signal (ORIS) and near-infrared spectroscopy (NIRS). ORIS is used to visualize the immediate hemodynamic changes in cortical areas following the stimulation, whereas NIRS measures the hemodynamic changes originating from subcortical areas. We found strong hemodynamic changes in relation to DCES both in ORIS and NIRS data. In particular, the signals originating from cortical areas exhibited a tri-phasic response, whereas those originating from subcortical regions exhibited multi-phasic responses. In addition, NIRS signals from two different sets of source-detector separation were compared and analyzed to investigate the causality of perfusion, which demonstrated downstream propagation, indicating that the upper brain region reacted faster than the deep region.
    Optics Express 03/2012; 20(7):6932-43. · 3.55 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The distribution of partial oxygen pressure (pO(2)) is analyzed for the anterior aspect of the left wrist with an amperometric oxygen microsensor composed of a small planar Pt disk-sensing area (diameter = 25 μm). The pO(2) levels vary depending on the measurement location over the wrist skin, and they are systematically monitored in the analysis for both one-dimensional single line (along the wrist transverse crease) and two-dimensional square area of the wrist region. Relatively higher pO(2) values are observed at certain area in close proximity to the position of acupuncture points with statistical significance, indicating strong relationship between oxygen and acupuncture point. The used oxygen microsensor is sensitive enough to detect the pO(2) variation depending on the location. This study may provide information helpful to understand possible physiological roles of the acupuncture points.
    Evidence-based Complementary and Alternative Medicine 01/2012; 2012:106762. · 1.72 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Location-dependent skin surface's partial nitric oxide pressure (pNO) is studied using highly sensitive amperometric NO microsensor with a small sensing area (diameter  = 76 μm). The pNO level of LI4 (Hegu) acupuncture point is measured and compared with the pNO level of nonacupuncture point. In addition, the mapping of pNO is carried out over the left wrist skin area one- as well as two-dimensionally. Statistically higher pNO levels near the position of acupuncture points than non-acupuncture points are observed consistently, implying tight relationship between the level of NO release of skin and acupuncture points. The amperometric planar NO microsensor successfully monitors the heterogeneity of skin pNO distribution in high spatial resolution due to its advantageous features such as high sensitivity and small sensing dimension. The current study suggests the direct connection between NO and acupuncture points and possibly provides beneficial information to understand physiological roles and basis of the acupuncture points.
    Evidence-based Complementary and Alternative Medicine 01/2012; 2012:781460. · 1.72 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: As gaseous nitric oxide (NO), a critical and multifaceted biomarker, diffuses easily once released, identifying the precise sources of NO release is a challenge. This study developed a new technique for real-time in vivo direct NO imaging by coupling an amperometric NO nanosensor with scanning electrochemical microscopy. This technique provides three-dimensional information of the NO releasing sites in an intact living mouse brain with high sensitivity and spatial resolution. Immunohistochemical analysis was carried out to confirm the anatomical reliability of the acquired electrochemical NO image. The real-time NO imaging results were well matched with the corresponding immunohistochemical analysis of neuronal NO synthase immunoreactive (nNOS-IR) cells, i.e., NO releasing sites in a living brain. The imaged NO local concentrations were confirmed to be closely related to the location in depth, the size of the nNOS-IR cell, and the intensity of nNOS immunoreactivity. This paper demonstrates the first direct electrochemical NO imaging of a living brain.
    Analytical Chemistry 09/2011; 83(21):8314-9. · 5.70 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: A melanoma tumor is a representative malignant tumor. Melanoma tumor growth involves vigorous angiogenesis around the tumor and a vasculogenic-like network inside an aggressive tumor. Primo vessels (PVs) are also found on the surface of the tumor and coexist alongside blood vessels (BVs), and sometimes within the BVs. We hypothesized that the primo vessels system plays a significant role in regulating the development of a melanoma tumor, and therefore has a tight coupling with BVs and angiogenesis. To prove this hypothesis, we developed a murine melanoma model by inoculating melanoma cell lines into the abdominal region. We used a green fluorescent protein (GFP) expressing mouse as a host to distinguish the endogenous source of the tumor PVs. We found strong formation of PVs on the tumor that coexisted with BVs and expression of GFP. PVs also had a tight coupling with adipose tissues, especially with white adipose tissue. These data suggest that the PVs of an induced melanoma tumor evolve endogenously from the host body and may be highly related to BVs and adipose tissue. This model of PVs in an overexpressing GFP mouse is a useful system for observing PVs, primo nodes, and primo vessel networks, and has potential to be developed as a model for examining novel treatments for cancer metastasis.
    Journal of acupuncture and meridian studies. 09/2011; 4(3):198-202.
  • [Show abstract] [Hide abstract]
    ABSTRACT: Murine melanoma requires the complex development of lymphatic, vascular, and non-vascular structures. A possible relationship between the primo vascular system (PVS) and the melanoma metastasis has been proposed. In particular, the PVS may be involved in oxygen transport. Vasculogenic-like networks, similar to the PVS, have been found within melanoma tumors, but their functional relationship with the PVS and meridian structures are unclear. Herein, we report on the use of an electrochemical O(2) sensor to study oxygenation levels of melanoma tumors in mice. We consistently found higher tissue oxygenation in specific sites of tumors (n=5). These sites were strongly associated with vascular structures or the PVS. Furthermore, the PVS on the tumor surface was associated with adipose tissue. Our findings suggest that the PVS is involved in the regulation of metastasis.
    Journal of acupuncture and meridian studies. 09/2011; 4(3):159-63.
  • [Show abstract] [Hide abstract]
    ABSTRACT: Nitric oxide (NO) is an important biomolecule for regulating various brain functions, such as the control of neurovascular tone. NO, however, cannot be stored inside cells where NO is produced and immediately diffuses through the cellular membrane and decays rapidly, which makes the detection of NO extremely hard in an in vivo setting. We constructed an amperometric NO nanosensor and utilized it to directly measure NO release in the living brain. The NO nanosensor uses nanopores (pores with an opening radii <500 nm) in which NO is oxidized at the porous platinum surface. The nanopore-based sensor was inserted vertically into the brains of anesthetized mice up to the end of the hippocampal CA 3 region, or to a depth of about 3mm. The sensor was slowly advanced in the brain in 0.5 μm increments and in 0.05 s temporal steps. Different levels of NO release were monitored by the nanopore NO sensor during the course of the penetration. The hippocampal CA3 region had the highest level of NO release, which was followed by CA2 and CA1 of the hippocampus and the cortex. The levels of NO release were not uniformly distributed within the cortical and hippocampal areas of living brain. In sum, the nanopore-based NO sensor was able to grossly measure NO contents within living brain in real time and with high sensitivity. This study may provide good insights about the relationship between the distributions of NOS-immunoreactive neurons and the directly measured levels of NO release in brain.
    Neuroscience Letters 07/2011; 498(1):22-5. · 2.03 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: In mild traumatic brain injury (mTBI), the fiber tracts that connect the frontal cortex with the cerebellum may suffer shear damage, leading to attention deficits and performance variability. This damage also disrupts the enhancement of eye-target synchronization that can be affected by cognitive load when subjects are tested using a concurrent eye-tracking test and word-recall test. We investigated the effect of cognitive load on eye-target synchronization in normal and mTBI patients using the nonlinear dynamical technique of stochastic phase synchronization. Results demonstrate that eye-target synchronization was negatively affected by cognitive load in mTBI subjects. In contrast, eye-target synchronization improved under intermediate cognitive load in young (≤40years old) normal subjects.
    Brain research 06/2011; 1398:55-63. · 2.46 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: In this paper, we propose a new array-type transcranial direct current stimulation (tDCS) system, which can modulate cortical excitability of human brain in a more effective manner. Once a target location inside a brain is determined, optimal injection current/potential at each electrode is calculated automatically by solving a constrained optimization problem. Current density distribution in a realistic head model was evaluated using the 3-D finite element method (FEM) adopting the superposition principle. Simulation results demonstrated that the proposed tDCS system enables effective and accurate field concentration on targeted brain areas.
    IEEE Transactions on Magnetics 06/2011; · 1.42 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Precise identification of epileptogenic zones in patients with intractable drug-resistant epilepsy is critical for successful epilepsy surgery. Numerous source-imaging algorithms for localizing epileptogenic zones based on scalp electroencephalography (EEG) and magnetoencephalography (MEG) have been developed and validated in simulation and experimental studies. Recently, intracranial EEG (iEEG)-based imaging of epileptogenic sources has attracted interest as a promising tool for presurgical evaluation of epilepsy; however, most iEEG studies have focused on localization of epileptogenic zones in focal epilepsy. In the present study, we investigated whether iEEG source imaging is a useful supplementary tool for identifying extended epileptogenic sources in secondary generalized epilepsy such as Lennox-Gastaut syndrome (LGS). To this end, we applied four different cortical source imaging algorithms, namely minimum norm estimation (MNE), low-resolution electromagnetic tomography (LORETA), standardized LORETA (sLORETA), and L(p)-norm estimation (p = 1.5, referred to as Lp1.5), to artificial iEEG datasets generated assuming various source sizes and locations. We also applied these four algorithms to clinical ictal iEEG recordings acquired from a pediatric patient with LGS. Interestingly, the traditional MNE algorithm outperformed the other imaging algorithms in most of our experiments, particularly in cases when larger-sized sources were activated. Although sLORETA outperformed both LORETA and Lp1.5, its performance was not as good as that of MNE. Compared to the other algorithms, the performance of Lp1.5 decayed most rapidly as the source size increased. Our findings suggest that iEEG source imaging using MNE is a promising auxiliary tool for the identification of epileptogenic zones in secondary generalized epilepsy. We anticipate that our results will provide useful guidelines for selection of an appropriate imaging algorithm for iEEG source imaging studies.
    Brain Topography 03/2011; 24(2):91-104. · 3.67 Impact Factor
  • Sleep Medicine 01/2011; 12(3):306-7. · 3.49 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The aim of this study is to investigate regional cerebral blood flow (rCBF) in patients with syncope. We compared brain single photon emission computed tomography (SPECT) images of neurally mediated syncope patients with those of age/sex matched healthy volunteers. (99m)Tc-ethylcysteinate dimer (ECD) brain SPECT was performed in 35 patients (M/F = 17/18, mean 36.6 years) with syncope during the asymptomatic period, and in 35 healthy volunteers. For statistical parametric mapping (SPM) analysis, all SPECT images were spatially normalized to the standard SPECT template and then smoothed using a 14-mm full width at half maximum Gaussian kernel. The mean duration of syncope history was 4.9 years and the mean number of syncope episodes was 6.3. In all patients, syncope or presyncope episodes occurred during head-up tilt tests, and all were the vasodepressive type. SPM analysis of brain SPECT images showed significantly decreased rCBF in the right anterior insular cortex, left parahippocampal gyrus, bilateral fusiform gyri, bilateral middle and inferior temporal gyri, left lingual gyrus, bilateral precuneus and bilateral posterior lobes of the cerebellum in syncope patients at a false discovery rate corrected p < 0.05. There were no brain regions that showed increased rCBF in syncope patients. Furthermore, we found a negative correlation between the total number of syncopal episodes and the rCBF of the right prefrontal cortex, and between the duration of syncope history and the rCBF of the right cingulate gyrus at uncorrected p < 0.001. Decreases of rCBF in multiple brain regions may be responsible for autonomic dysregulation and improper processing of emotional stress in neurally mediated syncope patients, and frequent syncope episodes may lead to frontal dysfunction.
    Journal of Neurology 10/2010; 258(3):366-72. · 3.58 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: This paper reports a real-time study of the codynamical changes in the release of endogenous nitric oxide (NO) and oxygen (O(2)) consumption in a rat neocortex in vivo upon electrical stimulation using an amperometric NO/O(2) dual microsensor. Electrical stimulation induced transient cerebral hypoxia due to the increased metabolic demands that were not met by the blood volume inside the stimulated cortical region. A NO/O(2) dual microsensor was successfully used to monitor the pair of real-time dynamic changes in the tissue NO and O(2) contents. At the onset of electrical stimulation, there was an immediate decrease in the cortical tissue O(2) followed by a subsequent increase in the cortical tissue NO content. The averages of the maximum normalized concentration changes induced by the stimulation were a 0.41 (±0.04)-fold decrease in the O(2) and a 3.6 (±0.9)-fold increase in the NO concentrations when compared with the corresponding normalized basal levels. The peak increase in NO was always preceded by the peak decrease in O(2) in all animals (n = 11). The delay between the maximum decrease in O(2) and the maximum increase in NO varied from 3.1 to 54.8 s. This rather wide variation in the temporal associations was presumably attributed to the sparse distribution of NOS-containing neurons and the individual animal's differences in brain vasculatures, which suggests that a sensor with fine spatial resolution is needed to measure the location-specific real-time NO and O(2) contents. In summary, the developed NO/O(2) dual microsensor is effective for measuring the NO and O(2) contents in vivo. This study provides direct support for the dynamic role of NO in regulating the cerebral hemodynamics, particularly related to the tissue oxygenation.
    Analytical Chemistry 09/2010; 82(18):7618-24. · 5.70 Impact Factor

Publication Stats

304 Citations
118.05 Total Impact Points

Institutions

  • 2011–2013
    • Sungkyunkwan University
      • • Institute of Basic Science
      • • Department of Biological Science
      • • Department of Neurology
      Sŏul, Seoul, South Korea
    • University of Missouri - St. Louis
      • Department of Physics and Astronomy
      Saint Louis, MI, United States
  • 2012
    • Korea University
      • Department of Biomedical Engineering
      Seoul, Seoul, South Korea
  • 2010–2012
    • Ewha Womans University
      • Department of Chemistry Nano Science
      Seoul, Seoul, South Korea
  • 2007–2009
    • New York Presbyterian Hospital
      • Department of Neurological Surgery
      New York City, New York, United States
  • 2004–2008
    • Weill Cornell Medical College
      • Department of Neurological Surgery
      New York City, New York, United States